North American P-51 Mustang

The Mustang did not begin as an American military requirement but as a commercial negotiation. In 1938 the British government set up a purchasing commission in the United States under Sir Henry Self, charged among other things with organising the supply of American fighters to the Royal Air Force. The choice was thin: no US aircraft then in production met European standards, and the closest, the Curtiss P-40 Tomahawk, came from a plant already running at capacity.

North American Aviation was supplying the RAF with its T-6 Texan trainer, known in British service as the Harvard, and was otherwise underused. When its president, James H. Kindelberger, approached Self to sell him a medium bomber, the B-25 Mitchell, the commission answered with a different question: could North American build P-40s under licence from Curtiss? Kindelberger replied that with the same Allison V-1710 engine his company could have a better aeroplane in the air sooner than it could set up a P-40 line. That refusal is where the Mustang starts.

Between January and April 1940 John Attwood spent long stretches at the commission's New York offices, working the concept out with British engineers through freehand sketches. Self, wary of a company with no fighter in its record, insisted that North American buy and study the P-40 drawings and wind tunnel data before submitting a detailed design. The company paid Curtiss 56,000 pounds for them and confirmed the purchase with the commission; Curtiss engineers would later accuse North American of plagiarism. With the detailed drawings approved, the project formally began on 4 May 1940 and a firm order for 320 aircraft followed on 29 May, replacing what until then had been only a letter of intent. The British terms were demanding: four 7.7 mm machine guns as on the Tomahawk, a unit cost no higher than 40,000 dollars, and the first production aircraft delivered by January 1941.

The design team, led by chief engineer Edgar Schmued, followed the best conventional practice of the day and planned from the outset for mass production: the three-section semi-monocoque fuselage and the two wing halves were split into five major assemblies, each wired and plumbed before being joined. Onto that conventional structure went two decisive novelties.

The first was a wing built around laminar-flow aerofoils developed jointly by North American and the NACA, offering very low drag at speed. Two wings were tested against each other in the University of Washington's Kirsten wind tunnel, one using five-digit NACA sections and one using the new NAA/NACA 45-100 sections; the latter won.

The second was the cooling installation, a single ducted water and oil radiator assembly set well aft, which cut fuselage drag and its interference with the wing. After much development it emerged that the arrangement could exploit the Meredith effect, the heated air leaving the radiator with a slight amount of jet thrust. Lacking a suitable tunnel of its own, North American used the three-metre GALCIT tunnel at the California Institute of Technology. Because the company had bought the complete Curtiss wind tunnel and flight test material, credit for the Mustang's cooling aerodynamics remained disputed for years. The NA-73X was also among the first aircraft whose fuselage was lofted mathematically using conic sections, which gave smooth, low-drag surfaces.

The prototype was rolled out in September 1940, 102 days after the order, and first flew on 26 October with Vance Breese at the controls, 149 days into the contract: an uncommonly short development even for wartime. It was built entirely of 24S aluminium alloy to save weight and armed with four 7.62 mm guns in the wings plus two 12.7 mm guns under the engine, synchronised to fire through the propeller arc.

The British order had specified an engine free of any export-sensitive turbocharger or multi-stage supercharger, so the Mustang I's Allison V-1710 had a single-stage blower whose output fell away sharply above 15,000 feet (4,600 m). The aircraft was superb low down and mediocre exactly where the European air war was being fought.

Allison's underfunded work on a high-altitude engine produced the V-1710-45, good for 1,150 horsepower (860 kW) at 22,400 feet (6,800 m); North American looked at fitting it in November 1941, but its excessive length meant extensive airframe changes and long production delays. The answer came from elsewhere. In May 1942, with favourable RAF reports on the Mustang I below 15,000 feet in hand, Rolls-Royce test pilot Ronald Harker proposed the Merlin 61, the Spitfire Mk IX engine, with the two-speed, two-stage intercooled supercharger designed by Stanley Hooker. The figures made the case: the Merlin 61 and the V-1710-39 both reached about 1,570 horsepower (1,170 kW) war emergency power at low level, but the Merlin gave 1,390 horsepower (1,040 kW) at 23,500 feet (7,200 m) against the Allison's 1,150 horsepower (860 kW) at 11,800 feet (3,600 m), lifting estimated top speed from 630 km/h at around 4,600 m to 710 km/h at 28,100 feet (8,600 m).

Rolls-Royce's airfield at Hucknall became the laboratory. A close working relationship grew there between North American, the RAF's Air Fighting Development Unit and the Rolls-Royce flight test establishment, and there five Mustang Mk I airframes became the Mustang X prototypes. In the event the Merlin 61 was never fitted to a Mustang at all: all five Mustang X conversions used the medium-altitude 65 series. The first flights were completed at Hucknall in October 1942.

The project had an outspoken champion. Major Thomas Hitchcock, assistant US air attache in London, put the USAAF's indifference on paper in a much-quoted passage: sired by the English out of an American mother, the Mustang had no parent in the Army Air Corps to appreciate and push its good points, and did not fully satisfy people on either side of the Atlantic who preferred to point with pride at a wholly national product. After Hitchcock's pressure, Rolls-Royce's calculations and a visit to Britain by a North American delegation that included Schmued, a contract for two American Merlin prototypes was let in July 1942, briefly designated XP-78 and almost at once XP-51B. With the Packard V-1650-3, a licence copy of the Merlin 61, North American estimated 716 km/h at 28,000 feet (8,500 m) and a service ceiling of 42,000 feet (13,000 m).

The first XP-51B flew in November 1942, but the USAAF was already convinced enough to have placed an initial contract for 400 aircraft three months earlier, in August. P-51B production started at Inglewood, California, in June 1943, and the type began reaching the Eighth and Ninth Air Forces in the winter of 1943-1944. The two-stage Merlin 60 series, over 160 kg heavier than the single-stage Allison and driving a four-blade Hamilton Standard propeller, required the wing to be moved slightly forward to correct the centre of gravity. When the USAAF directed fighter manufacturers in July 1943 to maximise internal fuel, that re-centring let North American add an 85 US gallon (320 L) tank behind the pilot. Everything else depended on that detail. The tank became standard on the P-51B-10 and was supplied as a retrofit kit for aircraft already built.

The definitive P-51D changed to the Packard V-1650-7, the two-speed two-stage Merlin 66, introduced the bubble canopy that solved the poor rearward view, and carried six 12.7 mm AN/M2 Browning machine guns.

The Mustang's first operator was the RAF, and its first aircraft were not P-51s at all: built to British requirements, they carried factory numbers, 320 NA-73s followed by 300 NA-83s, and were all designated Mustang Mark I. The first reached Britain in October 1941 and No. 26 Squadron brought them into service in January 1942. Poor high-altitude performance sent them to Army Co-operation Command rather than Fighter Command, on tactical reconnaissance and ground attack. They flew over France for the first time on 10 May 1942 near Berck-sur-Mer, and on 27 July sixteen of them made the first long-range reconnaissance sortie over Germany. Four British and Canadian Mustang squadrons, No. 26 among them, covered the Dieppe landing on 19 August 1942, and through 1943-1944 British Mustangs were used extensively to hunt V-1 flying bomb sites.

On low-level Rhubarb sorties the Mustang was in its element. The V-1710 ran smoothly at 1,100 rpm against the Merlin's 1,600, allowing long over-water legs at fifty feet before the enemy coast; over land the aircraft zig-zagged, turning every six minutes to defeat interception plotting. In the first eighteen months of these operations Mustang Mk I and Mk Ia aircraft destroyed or badly damaged 200 locomotives and more than 200 canal barges, along with an unknown number of aircraft caught on the ground, for the loss of eight Mustangs. At sea level they could outrun everything they met. The RAF also extracted a marked low-level gain by removing or resetting the manifold pressure regulator to allow overboosting, reaching as much as 1,780 horsepower at 70 inches of mercury, where in December 1942 Allison approved only 1,570 horsepower at 60 inches for the V-1710-39.

The RAF later operated 308 P-51Bs and 636 P-51Cs as the Mustang Mk III, converting from late 1943 into early 1944, and 828 bubble-canopy aircraft, Mk IV (P-51D) and Mk IVa (P-51K). As all but the earliest came under Lend-Lease, Mustangs still on RAF charge at the end of the war were either returned to the USAAF on paper or retained for scrapping; the last were retired in 1947.

Prewar American doctrine held that the bomber would always get through. Despite RAF and Luftwaffe experience of daylight bombing, in 1942 the USAAF still believed that tightly packed bomber formations carried enough defensive firepower to look after themselves. Escort was a low priority, and when it was discussed in 1941 the P-38 Lightning seemed the obvious answer on speed and range. A single-engined fighter with a bomber's reach was thought an engineering impossibility.

The Eighth Air Force began operating from Britain in August 1942 and, at the small scale of those early months, ended the year with losses under two per cent across 26 operations. In January 1943 the Casablanca Conference produced the Combined Bomber Offensive, American day raids complementing RAF night attacks, and in June the Pointblank directive ordered the destruction of the Luftwaffe before the invasion. The German response came fast. Late in 1943 the Eighth pushed deep into Germany beyond escort range and paid for it: the Schweinfurt-Regensburg mission in August cost 60 B-17s out of 376, and the raid of 14 October lost 77 out of 291, twenty-six per cent of the attacking force.

Rather than abandon day bombing, the USAAF first tried the YB-40 gunship conversions, which failed, then returned to the P-38 and, from early 1943, considered the P-47 Thunderbolt and the P-51B as escorts. A July 1943 report called the P-51B the most promising aeroplane, with an endurance of four hours forty-five minutes on 184 US gallons (700 L) internal plus 150 US gallons (570 L) external fuel. In August an extra internal tank was fitted; longitudinal stability problems forced some compromise in performance with the tank full, resolved in practice by burning that fuel during the opening stages of a mission. Every Mustang destined for VIII Fighter Command would carry it.

When Pointblank resumed in early 1944 the picture had changed. Escort was layered, shorter-ranged P-38s and P-47s covering the early stages and handing over to the P-51s when they had to turn for home, so that cover was continuous. The Mustang was so plainly superior to earlier American designs that the Eighth steadily switched its groups, first trading newly arrived P-47 groups to the Ninth Air Force for those already flying Mustangs, then converting its own Thunderbolt and Lightning groups. By the end of 1944, 14 of its 15 groups flew Mustangs.

The decisive change was tactical. At the start of 1944 Major General James Doolittle, the new commander of the Eighth, released most of his fighters from close formation with the bombers and let them seek out the Luftwaffe wherever it could be found. Mustang groups ranged far ahead on fighter sweeps. Bomber crews complained; by June air supremacy had been won.

The twin-engined Bf 110 Zerstorer heavy fighters brought up against the bombers proved easy prey and had to be withdrawn. The Fw 190A, already weak at altitude, was outperformed by the Mustang at B-17 height, and when loaded with heavy bomber-killing weapons and extra armour it lost manoeuvrability and suffered severely. The Bf 109 could match the P-51 high up, but its light airframe suffered even more from added armament. The Luftwaffe answered with the Gefechtsverband, a Sturmgruppe of heavily armed and armoured Fw 190As escorted by two Begleitgruppen of Bf 109s whose job was to keep the Mustangs off. The formation took a long time to assemble and was hard to manoeuvre, and P-51 sweeps often broke it up before it reached the bombers; when the attacks did go in, however, the Fw 190s came from astern and often pressed to within ninety metres.

The threat of those mass attacks, and later of company front assaults eight abreast, made destroying the Luftwaffe on the ground as urgent as beating it in the air. From late February 1944 Eighth Air Force fighter units began systematic strafing of German airfields, at first on the way home from escort duty and from March as assigned missions in their own right. The P-51, helped by the K-14 gyro gunsight and the intensive Clobber Colleges pilot training of late 1944, was decisive in these countermeasures. On 15 April 1944 VIII Fighter Command opened Operation Jackpot against Luftwaffe fighter fields; on 21 May the target list widened to railways, locomotives and rolling stock in the missions known as Chattanooga. The Mustang excelled at this work but paid for it: strafing losses far exceeded air combat losses, because the liquid-cooled Merlin was highly vulnerable to small-arms damage to radiator and coolant lines, while the air-cooled radial P-47 could shrug such fire off and took over much of the low-level work.

The Luftwaffe sought refuge in extreme performance. The Me 163B rocket interceptor began operations with JG 400 at the end of July 1944 and proved more dangerous to its own side than to the Allies; the Me 262A jet, which reached the front with the Kommando Nowotny by the end of September, was a serious threat, but its Jumo 004 engines needed careful nursing and the aircraft was helpless on take-off and landing. Lieutenant Chuck Yeager of the 357th Fighter Group was among the first Americans to shoot one down, catching it on approach; on 7 October 1944 Lieutenant Urban L. Drew of the 361st destroyed two as they took off, and on 25 February 1945 Mustangs of the 55th Fighter Group surprised an entire Staffel of Me 262s at take-off and destroyed six.

By 8 May 1945 the P-51 groups of the Eighth, Ninth and Fifteenth Air Forces claimed some 4,950 aircraft shot down, about half of all USAAF claims in the European theatre and the highest total of any Allied fighter in air-to-air combat, along with 4,131 destroyed on the ground, for losses of about 2,520 aircraft. The leading units in the air were the Eighth's 357th Fighter Group with 565 victories and the Ninth's 354th with 664. The top Mustang ace was George Preddy, whose final tally of 26.83 victories included shared credits and 23 scored on the P-51; he was shot down and killed by friendly fire on Christmas Day 1944 during the Battle of the Bulge.

Two Mustang pilots received the Medal of Honor. Lieutenant Colonel James H. Howard of the 356th Fighter Squadron earned his near Oschersleben on 11 January 1944, when, heavily outnumbered, he shot down three German aircraft and went on defending the bombers after his guns failed and his fuel ran dangerously low, flying P-51B 43-6315 Ding Hao. Major William A. Shomo of the 82nd Reconnaissance Squadron received his for a mission over Luzon on 11 January 1945, when he shot down seven Japanese aircraft in a single sortie flying an F-6D, the armed photo-reconnaissance version of the Mustang.

In early 1945 P-51C, D and K variants joined the Chinese Nationalist Air Force, equipping its 3rd, 4th and 5th Fighter Groups against Japanese targets in occupied China. The Mustang became the most capable fighter in that theatre, where its principal opponent was the Nakajima Ki-84 Hayate.

It arrived late in the Pacific, both because Europe had priority and because the twin-engined P-38 was considered safer over long stretches of water. The first P-51s deployed to the Far East late in 1944 on close support, escort and tactical photo-reconnaissance. The capture of Iwo Jima changed the scale: from March 1945 VII Fighter Command Mustangs flew from the island escorting B-29s against the Japanese home islands. Extreme humidity and blowing volcanic dust made maintenance hard, and holding minimum power settings for hours to stretch the range fouled the spark plugs with lead, so they had to be replaced after every mission. These were round trips of 1,500 miles, mostly over water with minimal navigation equipment, lasting seven or eight hours. Where 110 US gallon (420 L) drop tanks served over Europe, missions to Japan often used 165 US gallon (620 L) tanks for more loiter time. The B-29s did not fly in combat boxes like the European B-17s and B-24s but in a stream that could stretch 200 miles; the escorts covered it with three target combat air patrol squadrons, two on one side and one on the other, each 2,000 feet above and 4,000 to 5,000 feet out from the bomber stream.

Against its Japanese opponents the Mustang generally held the advantage. The A6M Zero, the most numerous Japanese fighter, was poor at altitude, precisely where the P-51 was best, though on low and medium level interdiction work the Zero could still out-turn and out-climb it. Newer designs were potent but scarce: the Kawanishi N1K-J Shiden was fast and agile but a poor interceptor because of its weak climb, and the Ki-84 could match the P-51 on performance and ceiling but suffered manufacturing defects and a demanding Homare engine starved of high-octane fuel.

In practice escort proved unnecessary, and only ten such missions were flown from Iwo Jima. The interceptor threat kept fading, the bombing campaign had shifted from daylight precision attacks to night incendiary raids, and Japan was hoarding aircraft and fuel for kamikaze use. The command's last major May raid was the daylight incendiary attack on Yokohama of 29 May, with 517 B-29s escorted by 101 P-51s and intercepted by 150 Zeros: five bombers were shot down and 175 damaged, while the Mustang pilots claimed 26 kills and 23 probables for three fighters lost. On 1 June, later known as Black Friday, 521 B-29s escorted by 148 P-51s were sent against Osaka; the Mustangs flew into thick cloud and 27 were lost in collisions, though 27 more and 458 bombers reached the city.

The Mustangs also fought a war of their own. The first independent ground-attack operation came on 16 April, when 57 P-51s strafed Kanoya airfield on Kyushu. Between 26 April and 22 June the pilots claimed 64 aircraft destroyed and 180 damaged on the ground, plus ten shot down in the air, results below expectations that led the raids to be judged unsuccessful; losses were 11 P-51s to enemy action and seven to other causes. From July, with no air opposition left, VII Fighter Command flew ground attack alone, largely against airfields where aircraft were being held back for the expected invasion fleet and defended by anti-aircraft batteries and barrage balloons. By the end of the war it had flown 51 ground-attack raids, 41 of them considered successful, claiming 1,062 aircraft destroyed or damaged and 254 ships, at a cost of 91 pilots killed and 157 Mustangs lost. In all, the very long range campaign from Iwo Jima ran to 51 missions and 4,172 sorties over Japan, with enemy aircraft encountered on 33 occasions.

Captain Eric Brown, chief naval test pilot and commanding officer of the Captured Enemy Aircraft Flight, tested the Mustang at Farnborough in March 1944 and left the most quoted verdict on the type: it was a good fighter and the best escort because of its extraordinary range, and the best American dogfighter, but the laminar-flow wing could be tricky and it could not out-turn a Spitfire by any means, though it rolled better. In a dogfight he would rather have the Spitfire, he concluded, except that he would not want to be in a dogfight near Berlin, because in a Spitfire he could never get home. The US Air Forces flight test engineering office assessed the Mustang B on 24 April 1944 in similar terms: good rate of climb, exceptionally good level speed from sea level to 40,000 feet, very manoeuvrable with good controllability up to 400 mph indicated, good stability about all axes and excellent roll rate, but a fairly large turning radius for a fighter and poor visibility on the ground, only fair in level flight.

From the other side, Kurt Buhligen, the third highest scoring German fighter pilot of the Western Front with 112 confirmed victories, summed it up by saying that the Bf 109 and Fw 190 could out-turn the P-51 and the other American fighters, that the P-51 was faster but that German ammunition and cannon were better. Heinz Bar called the Mustang perhaps the most difficult of all Allied aircraft to meet in combat: fast, manoeuvrable, hard to see and hard to identify, because it resembled the Me 109.

Apart from the small Australian series, every Mustang was built by North American, first at Inglewood, California, and then also at Dallas, Texas, with the suffixes -NA and -NT respectively. North American built 15,588 airframes in total, including the 100 shipped unassembled to Australia; the summary infobox of that same source gives 15,686 and the Smithsonian speaks only of more than 14,000 Mustangs, so the exact total varies with the count.

The bulk was the P-51D at 8,200 aircraft, 6,600 from Inglewood and 1,600 from Dallas, followed by 1,987 P-51Bs, 1,750 P-51Cs, the first variant built at Dallas and identical to the B, and 1,500 P-51Ks, identical to the D except for the four-blade Aeroproducts propeller. Before them came 620 Mustang Is for the RAF, 500 A-36 Apache dive bombers, 150 P-51s, of which 93 went to Britain as the Mustang Ia and 57 were retained by the USAAF with V-1710-39 engines, and 310 P-51As, 50 of them Lend-Leased to the RAF as the Mustang II. The lightweight family produced three XP-51Fs, two XP-51Gs with five-blade propellers and two Allison-engined XP-51Js, and from it came the P-51H, of which 555 were built at Inglewood. A single P-51M was completed. To the prototypes belong the NA-73X, two XP-51s, two XP-51Bs and three XP-51Ds.

In Australia the Commonwealth Aircraft Corporation assembled 80 CA-17 Mustang Mk 20s from the kits received, out of the 100 shipped, and licence-built 120 CA-18 Mk 21, Mk 22 and Mk 23 aircraft of the 170 originally ordered, using the Packard V-1650-3 or -7 except on the Mk 23, which took a Rolls-Royce Merlin 66 or 70: 200 aircraft in all. Conversions included at least five field-modified dual-control TP-51Cs, a single ETF-51D adapted for carrier trials and the five Rolls-Royce Mustang X prototypes, whose planned run of 500 was cancelled once the Packard-engined P-51B/C prevailed. Cancelled outright were the NA-133, a navalised P-51H with folding wings, arrestor hook and tip tanks, the lightweight P-51L and 250 two-seat CAC CA-21 Mustang Mk 24s.

With the war over, the USAAF consolidated its combat force and chose the P-51 as its standard piston-engined fighter while the P-38 and P-47 were withdrawn or reduced to secondary roles; the arrival of the P-80 and P-84 jets then pushed the Mustang into secondary duties in turn. In 1947 the new Strategic Air Command used fighter Mustangs alongside F-6s and F-82 Twin Mustangs precisely for their range. The 1948 designation scheme changed the pursuit prefix P- to the fighter prefix F- and moved the old photo-reconnaissance F- to RF-, so surviving versions became the F-51B, F-51D, F-51K, RF-51D, RF-51K and TRF-51D. By 1950 most USAF Mustangs were surplus, in storage or transferred to the Air Force Reserve and the Air National Guard.

Korea brought them back. A substantial number of stored and in-service F-51Ds were shipped by carrier to the combat zone for the USAF, the South African Air Force and the Republic of Korea Air Force, used for ground attack with rockets and bombs and for photo-reconnaissance rather than as interceptors or pure fighters, roles in which early jets had already surpassed them. With American units forced to fly from Japan after the first North Korean invasion, the F-51D's range let it strike targets the short-legged F-80 could not reach; in exchange, its liquid cooling system made it very vulnerable to ground fire and losses were heavy. On 5 August 1950 Major Louis J. Sebille of the 67th Fighter-Bomber Squadron attacked a North Korean armoured column during the Pusan Perimeter battle; wounded and with his aircraft badly damaged on the first pass, he turned back and deliberately crashed into the convoy, and was awarded the Medal of Honor posthumously. Mustangs flew close support and interdiction with the USAF and ROKAF until 1953, when F-84s and Navy F9F Panthers largely replaced them. The Royal Australian Air Force's 77 Squadron, flying Australian-built Mustangs with the Commonwealth forces, converted to Gloster Meteor F8s in 1951.

At home F-51s served with the Reserve and the Air National Guard through the 1950s. The last in that role was F-51D-30-NA 44-74936, withdrawn from the West Virginia Air National Guard's 167th Fighter Interceptor Squadron in January 1957 and retired to what was then the Air Force Central Museum, though it flew again briefly on 6 May 1957 at the fiftieth anniversary of the Air Force aerial firepower demonstration at Eglin. It is displayed today at the National Museum of the United States Air Force at Wright-Patterson, painted as 44-15174.

Withdrawal put hundreds of P-51s on the civil market. The design rights were bought from North American by the Cavalier Aircraft Corporation, which set out to sell the surplus at home and abroad. In 1967 and again in 1972 the USAF ordered batches of remanufactured Mustangs from Cavalier, most intended for South American and Asian air forces in the Military Assistance Program: original F-51D airframes with new V-1650-7 engines, new radios, the tall F-51H fin and a stronger wing carrying six 12.7 mm guns and eight underwing hardpoints for two 450 kg bombs and six 127 mm rockets, with an F-51D canopy but a second seat for an observer. One two-seat dual-control TF-51D with an enlarged canopy and only four guns was also built.

The last American military use came in 1968, when the US Army flew a veteran F-51D as a chase aircraft on the Lockheed YAH-56 Cheyenne attack helicopter programme. It worked so well that two more were ordered from Cavalier for Fort Rucker, unarmed and fitted with wingtip tanks; one was later tested with a 106 mm recoilless rifle against fortified ground targets, and the other survives at the Air Force Armament Museum at Eglin in wartime markings.

After 1945 the Mustang served with the air arms of more than twenty-five nations. A wartime example cost about 51,000 dollars; many hundreds were sold afterwards for a nominal one dollar to signatories of the Inter-American Treaty of Reciprocal Assistance ratified at Rio de Janeiro in 1947.

Australia received its first in November 1944, when 3 Squadron RAAF, then in Italy with the Desert Air Force, gave up its P-40s; only 17 Mustangs reached front-line squadrons before the war ended, but the type equipped Citizen Air Force units until 1960 and, with 77 Squadron, fought in Korea. Canada flew Mustang Mk Is and Mk IIIs in five wartime squadrons and later bought 150 P-51Ds for two regular and six auxiliary squadrons, declared obsolete in 1956 though special-duty aircraft carried on into the early 1960s.

In China the Mustang changed sides twice. The Nationalist air force used it against Japan and then against the Communists, taking most of its aircraft to Taiwan in 1949, while the People's Liberation Army captured 39 and formed its first P-51 squadron at Beijing Nanyuan in August 1949; nine took part in the fly-past at the proclamation of the People's Republic on 1 October 1949. Once Soviet equipment arrived they went to the flying school, 13 converted as two-seat trainers, and by September 1953 only eight remained, used to teach Il-10 pilots to taxi.

Europe had its own postwar Mustang story. Sweden recovered four aircraft diverted to its territory during missions over Europe, bought 50 P-51Ds in February 1945 as the J 26 and added batches of 90 and 21 for a total of 161; about a dozen became S 26 photo-reconnaissance machines and took part in the secret Swedish mapping of new Soviet installations on the Baltic coast in 1946-1947, an effort involving many deliberate airspace violations from which none was lost, because the Mustang could out-dive any Soviet fighter of the day. Switzerland bought 130 aircraft at 4,000 dollars each and kept them until 1958. Italy received 173 examples under MDAP between September 1947 and January 1951 and spread them across all its fighter wings; some restrictions were imposed, since handling demanded care once the fuel tanks were emptied and several aerobatic manoeuvres were forbidden, but the P-51D was highly rated, partly because it arrived in far better condition than the other Allied types supplied. France began converting to reconnaissance Mustangs in late 1944 and flew F-6Cs and F-6Ds on photographic mapping over Germany from January 1945 until jets replaced them in the early 1950s. Five Polish squadrons in Britain flew Mustangs from 1942, beginning with 309 Squadron, and on disbandment between December 1946 and January 1947 returned about 80 Mk IIIs and 20 Mk IV/IVas to the RAF. The Soviet Union received at least ten ex-RAF Mustang Mk Is, judged them inferior to its own fighters and sent them to training units; later Lend-Lease P-51B/C and D aircraft, and machines left in Russia after the shuttle missions, were repaired and flown but never in front-line service.

Germany flew the type too, though not by choice: several P-51s captured after forced landings were repaired and tested at Gottingen by the Zirkus Rosarius, the Luftwaffe's official enemy aircraft evaluation unit, repainted in German markings with bright yellow noses, tails and bellies. Japan did the same with the P-51C-11-NT Evalina, hit by gunfire on 16 January 1945 and belly-landed at Japanese-held Suchon airfield in China, then repaired, roughly marked with hinomaru roundels and flown to the Fussa evaluation centre, today Yokota Air Base.

In Asia and Oceania, New Zealand ordered 370 Mustangs to supplement its Corsairs, but only the first 30 arrived, still crated when the war ended; they entered service in 1951 with four Territorial Air Force squadrons and were retired prematurely in August 1955 after undercarriage and coolant-system corrosion problems. The Philippines acquired 103 P-51Ds that became the backbone of its postwar air force, heavily used against the Huk insurgency and the Moro rebellion until 1955 and flown by the first Blue Diamonds display team; F-86s replaced them in the late 1950s, though some served in counter-insurgency roles into the early 1980s. The Netherlands flew 40 P-51Ds in the East Indies during the police actions of 1947 and 1948-1949, and 26 passed to Indonesia at the end of the conflict, which received 35 more from the United States in 1960-1961 and used them against the rebellions of the 1950s; on 18 May 1958 a P-51D flown by Captain Ignatius Dewanto shot down Allen Lawrence Pope's B-26 Invader near Ambon, the first and only aerial victory of the Indonesian air force. South Korea received ten F-51Ds within a month of the outbreak of war under the Bout One project, flown by Korean pilots, several of them veterans of the Japanese services, and American advisers led by Major Dean Hess; they formed the backbone of the ROKAF and flew with the Black Eagles display team until 1954. Israel bought a few Mustangs illegally in 1948, crated and smuggled in as agricultural equipment, and they quickly became the best fighters in its inventory; they were still in service at Suez, where four of them cut Egyptian telephone and telegraph wires with their wings in extreme low-level runs coordinated with the parachute drop at the Mitla Pass. South Africa flew Mustang Mk IIIs and Mk IVs in Italy from September 1944 with 5 Squadron and received American F-51Ds for 2 Squadron in Korea in 1950, replaced by F-86s in 1952 and 1953. Somalia operated eight P-51Ds.

Latin America was the type's last refuge. The Dominican Republic, the largest Latin American operator, gathered six aircraft in 1948, 44 ex-Swedish F-51Ds the same year and one more of unknown origin, and kept some flying until 1984; nine of the last ten were sold back to American collectors in 1988. Guatemala had 30 P-51Ds from 1954 into the early 1970s; Nicaragua bought 26 from Sweden in 1954 and later received 30 more plus two TF-51s under MAP, all retired by 1964; Uruguay flew 25 between 1950 and 1960 and sold some to Bolivia, which also received nine Cavalier F-51Ds under the Peace Condor programme; Costa Rica had four between 1955 and 1964; Haiti had four under President Paul Eugene Magloire, retired in 1973-1974 and sold to the Dominican Republic for spares. Cuba took delivery in November 1958 of three American civil P-51Ds flown illegally from Miami for the 26th of July Movement; one was damaged in transit and none saw action, and after the revolution the lack of spares and expertise left them grounded and eventually on museum display. El Salvador bought five Cavalier Mustang IIs and one dual-control TF-51 with tip tanks and uprated Merlins, and also operated seven P-51Ds; it used them in the 1969 Football War against Honduras, the last combat use of the type, in which FAS-404 was shot down by Captain Fernando Soto in a Vought F4U-5 Corsair in what is regarded as the world's last air combat between piston-engined fighters. The last Mustang downed in battle fell during Operation Power Pack in the Dominican Republic in 1965.

Many P-51s were sold as surplus for as little as 1,500 dollars, some to former wartime pilots and enthusiasts, others to be modified for air racing. The most significant racer was 44-10947, a surplus P-51C-10-NT bought by film stunt pilot Paul Mantz, who sealed the wings to turn each into a giant integral fuel tank and so do away with fuel stops and drag-inducing drop tanks. Named Blaze of Noon, it won the 1946 and 1947 Bendix races, took second in 1948 and third in 1949, and carried Mantz to a US coast-to-coast record in 1947. Sold to Charles F. Blair Jr and renamed Excalibur III, it set a New York to London record in 1951, about 3,460 miles or 5,570 kilometres, in 7 hours 48 minutes, and later that year flew from Norway to Fairbanks, Alaska, over the North Pole, about 3,130 miles or 5,040 kilometres, proving that navigation by sun sights was possible across the magnetic pole region. Blair received the Harmon Trophy, and the Air Force was obliged to rethink its assumptions about a Soviet strike from the north. The aircraft is now at the National Air and Space Museum's Steven F. Udvar-Hazy Center.

In 1958, when the RCAF retired its 78 remaining Mustangs, pilot Lynn Garrison ferried them one by one from storage to Canastota, New York, where the American buyers were waiting; those aircraft account for a large share of the Mustangs flying worldwide today. The most prominent civil converter was Trans-Florida Aviation, later the Cavalier Aircraft Corporation, whose Cavalier Mustang offered a taller fin, wingtip tanks and a tight second seat in the space once occupied by the military radio and fuselage fuel tank. In the late 1960s and early 1970s the Department of Defense paid Cavalier to return some of those civil conversions to updated military standard for supply to South American countries and Indonesia.

In the twenty-first century a P-51 can command more than a million dollars even when only partly restored. The FAA registry listed 204 privately owned P-51s in the United States in 2011, most of them still flying and often associated with organisations such as the Commemorative Air Force. The type still sets records: in May 2013 Doug Matthews reached 12,975 m in a P-51 named The Rebel, an altitude record for piston aircraft weighing between 3,000 and 6,000 kg, together with time-to-height records of 18 minutes to 9,000 m and 31 minutes to 12,000 m. That civil life has had its cost: among the remembered accidents are the crash that killed William Penn Patrick and his passenger at Lakeport, California, on 9 June 1973, the death of Harry E. Tope at the National Capital Air Show in Ottawa on 1 July 1990, and the loss of the heavily modified Galloping Ghost, which crashed beside the grandstand at the Reno races on 16 September 2011, killing pilot Jimmy Leeward and at least nine people on the ground.